The present invention relates to a mechanism for joining mullions to transoms in a curtain wall.
The primary purpose of the present invention is to provide a mechanism that enables simple on-site joining of mullions and transoms which are factory-fabricated as members of a curtain wall. This mechanism prevents water leakage from the joint between the mullion and transom. At the same time, it is capable of adjusting well to a lateral displacement between the mullion and transom, as well as to the thermal expansion and contraction of the transom.
The use of a pressure equalization system in a mullion type curtain wall has been gaining wider acceptance recently. According to this system, a space having a pressure almost equal to that of the atmosphere is created in both mullions and transoms, and the wind pressure of an incoming rain storm is eliminated in this space, and the rain water is drained by gravity, whereas the entrance of rain water into the building is prevented by a rain barrier provided between the pressure-equalized space and the inside of the building. Since the rain barrier is not provided on the outer surface of the curtain wall, this balanced pressure system claims significantly increased durability of the airproofing sealants (i.e. gaskets and caulking components) provided in the junctions of the rain barrier and protected from the elements. However, in a mullion type curtain wall, the airproofing sealants on the rain barrier consist of an internal sealant around a glass pane encased in the mullion and transom and a joint sealant laid along the joint between the mullion and transom, and gaskets and caulking compounds are carefully applied to the necessary sealing portions on site. Particularly, great care is needed in providing the joint between the mullion and transom with a hermetic seal that not only prevents water leakage but also adjusts well to lateral displacement between the two members and to the thermal expansion and contraction of the transom.
In the conventional method of assembling a curtain wall, a prefabricated mullion with an angular mounting member is shipped to the site, where an end of a transom is bolted to the mounting member. But this procedure, in addition to the installation of a hermetic seal in the joint between the mullion and transom, greatly increases the complexity of constructing the curtain wall.
These defects in the conventional technique for joining the mullion to a transom in a curtain wall construction are eliminated by the new joint mechanism of the present invention, described hereunder.